Question

Electron gain enthalpy values (\(\Delta_{eg}H\)) (in kJ mol\(^{-1}\)) of elements X, Y and Z are \(-349, -200\) and \(-295\) respectively. X, Y and Z are respectively

• A. Cl, I, S
• B. Cl, S, I
• C. S, Se, Te
• D. Na, K, Rb

Hint:

Chlorine has the most negative electron gain enthalpy. Fluorine is less negative than Chlorine due to small size and inter-electronic repulsion. The order for halogens is Cl>F>Br>I. Group 16 elements (S) are less negative than halogens.

Answer 1

The Correct Option is B

Step 1: Analyze the values The given electron gain enthalpies are: X: \(-349\) kJ/mol (Very high negative value, indicating Halogen, specifically Chlorine). Y: \(-200\) kJ/mol (Moderate negative value). Z: \(-295\) kJ/mol (High negative value, likely another Halogen).
Step 2: Compare with standard values - Chlorine (Cl): Has the highest negative electron gain enthalpy in the periodic table, approximately \(-349\) kJ/mol. This matches X. - Iodine (I): A halogen lower in the group, less negative than Cl. Value is approximately \(-295\) kJ/mol. This matches Z. - Sulfur (S): A group 16 element. Its electron gain enthalpy is around \(-200\) kJ/mol. This matches Y.
Step 3: Match with options We need X = Cl, Y = S, Z = I. This corresponds to the sequence Cl, S, I. Final Answer:
Cl, S, I.